System For Managing A Reagent Dispensing Device In An Exhaust Line

ABSTRACT

The invention relates to a system for managing a reagent dispensing device in the exhaust line of an engine, said circuit including a tank ( 1 ), an injection means ( 3 ), a means for conditioning the reagent, sensors capable of determining the representative parameters of the condition of the dispensing circuit and of the reagent, and actuators for controlling the conditioning and injection means driven by a calculation unit based on the condition of the dispensing circuit and of the reagent and on the engine parameters determined by an engine control unit ( 5 ) characterised in that the calculation unit is integrated in the engine control unit ( 5 ) and in that the system includes an analog/digital interface ( 4 ) for processing the analog signals from the sensors ( 2 ) and the actuators ( 3, 7, 8, 9 ), provided in the vicinity of the tank ( 1 ) and connected to the engine control unit by a multiplexed digital link.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage under 35 U.S.C. §371 of International Application No. PCT/FR2008/051401 which was filed on Jul. 25, 2008 and which, in turn, claims the priority to French patent application 0756936 which was filed on Aug. 3, 2007, the content of which (description, claims and drawings) is incorporated here by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a control system for a reagent dispensing device in an exhaust line.

The pollutants released by the combustion of an automobile engine, whether diesel or gasoline, are mainly unburned hydrocarbons HC, nitrogen oxides (nitrogen monoxide NO and nitrogen dioxide NO₂, more generally designated as NOx), carbon oxides (carbon monoxide CO) and solid carbonaceous particles in the case of lean burning diesel engines and direct injection gasoline engines.

Direct injection fuel systems and partial reintroduction of exhaust gas in the engine reduce the formation of certain pollutants in the combustion chamber. Nevertheless, post treatment systems for exhaust gas are indispensable to satisfy the more and more rigorous environmental standards.

In commercial vehicles, the treatment of exhaust gas of an internal combustion engine was limited, until now, to the use of catalytic converters for gasoline engines and particulate filters for diesel engines. Catalytic converters are very efficient in reducing the emissions of unburned hydrocarbons (HC) and carbon monoxide; particulate filters are very efficient for storing and destroying emissions of carbonaceous particles. To control NO_(x) emissions, gasoline engines are currently using so-called 3-way catalysts, but this type of catalyst loses practically all efficiency if the air-fuel mixture is lean, which is the case for diesel engines.

For this reason, other solutions were developed for diesel engines, among which a process called SCR catalysis (Selective Catalytic Reduction) which has a as principle the selective reduction of NO_(x) into nitrogen and water, in the presence of a specific catalyst and through the action of a reducing agent.

In this way, the reduction takes place in an environment containing excess air, such as the exhaust gas of an engine running on a lean mixture, with ammonia as typical reducing agent. The ammonia can be supplied through chemical decomposition of a reagent such as urea, injected in the exhaust line starting from a dedicated reservoir in which the urea is stored in the form of aqueous mixture.

To ensure proper vehicle autonomy, this reservoir must have sufficient volumetric capacity, for instance approximately twenty liters. Since it is not desirable to locate the reservoir in the engine compartment, nor in the cabin of the vehicle, it is generally recommended to mount the unit in the rear of the vehicle, in or under the trunk, since in most vehicles the engine is located under the front hood.

Located in the rear of the vehicle, this storage unit is far away from the engine control module. The injection of reagent requires perfect control of the injection device in the exhaust line associated with the storage unit, while taking into consideration the driving conditions of the vehicle, which implies a link with the control module dedicated to the operation of the engine.

A large number of electrical components is devoted to controlling the injection of the reagent, namely, a pump, a pressure sensor, a solenoid valve, a fluid level sensor, a temperature sensor, an injector and heating elements. The heating elements are included, because in the case of urea, the reagent commercialized under the name “Adblue”, freezes at temperatures lower than −11° C. (12° F.). All these components are controlled by the electronic control module of the SCR system, in relation with the information provided by the engine control module. The system requires a large number of electrical connections and in addition it must be noted that the key elements of the system are located as far away as possible in the vehicle.

For these installations, two types of architecture have been proposed:

According to the first concept, the control module of the internal combustion engine is used to perform the different exhaust gas treatment functions—this avoids using a dedicated electronic module for controlling the SCR system. This concept implies a rather significant size increase of the engine control module connector in order to integrate the various input and output signals exchanged with the different elements of the system. Since the engine control module is normally located in the engine compartment of an automotive vehicle and the means of the SCR system for treatment of exhaust gas are normally located in the rear of an automotive vehicle, this architecture requires several electrical wiring harnesses running between front and rear of the vehicle, which entails additional weight and significant system cost, namely the cost of developing and manufacturing the electrical wiring harnesses and significant assembly cost.

According to the second possible architecture, a dedicated control unit is used for handling the various exhaust gas treatment functions, and for controlling the various sensors and actuators of the system. The dedicated control unit is connected with the engine control module to exchange information with the engine that is necessary for controlling the injection of reagent. Therefore this concept requires the development of a dedicated control unit for the injection of reagent, which entails, besides the development cost of the dedicated control unit, the cost to assemble the control unit and the numerous cables, as well as, at least in certain cases, the cost to modify the body, the cabin or other components of the automotive vehicle in order to provide easy access to the location of the dedicated control unit, etc.

BRIEF SUMMARY OF THE CLAIMED INVENTION

The goal of the claimed invention is to propose a simple concept, and consequently, the least expensive in terms of development and assembly cost.

The goal of the claimed invention is achieved with a system for controlling a reagent dispensing circuit in the exhaust line of an engine. The circuit comprises a reservoir, injection means, reagent conditioning means, sensors suitable for determining parameters representing the status of the dispensing circuit and of the reagent, and actuators for controlling the conditioning and injection means. The actuators are controlled by a control unit in response to the status of the dispensing circuit and the status of the reagent and engine parameters as determined by the engine control module.

According to the claimed invention, the system control unit is integrated in the engine control module and the system comprises a digital/analog interface for processing the analog signals of sensors and actuators, which are mounted in the proximity of the reagent reservoir and are connected to the engine control module through a multiplexed digital link.

The control system according to the claimed invention uses only one control unit, the engine control module, and only one transmission wiring harness, the multiplexed digital interface. The digital/analog interface of the dispensing circuit is limited to a slave role controlled by the engine control module. This architecture is particularly advantageous for a dispensing system remotely located from the engine control module.

The device of the claimed invention contains various means dedicated to the different functions of the treatment device constituting an electronic interface and mechanical means. The electronic interface receives, from the engine control module command, signals for the mechanical actuators and consequently generates electrical signals for controlling these actuators. In addition, the electronic interface receives analog signals from the different sensors and diagnostic information from the different sensors and actuators and sends back to the engine control module digital information representing the values measured by the sensors and the diagnostic states of the different sensors and actuators.

The control strategy of the treatment device according to the claimed invention is implemented advantageously by specific software integrated in the software of the engine control module. The electronic interface of the invention device simply performs a slave role controlled by the engine control module, which eliminates the need to install a second control module while allowing the elimination of a multitude of electrical wiring harnesses.

The architecture of the claimed system allows for the connection between the different elements contributing to the treatment of exhaust gas to be simplified significantly.

In addition, the concept of the system or device simplifies the integration of exhaust gas treatment with the various elements of the automotive vehicle by the absence of a supplementary control unit and by limiting the number of supplementary electrical wires between the different electrical and mechanical elements, which represents significant gains in terms of cost, weight, quality and reliability relative to other concepts.

According to different implementation modes, the present invention also relates to the following characteristics considered in isolation or in any possible technical combination:

-   -   the multiplexed link is dedicated to the reagent dispensing         circuit;     -   the multiplexed digital link is a CAN network;     -   the dispensing system comprises at least one sensor for the         temperature of the reagent in the reservoir;     -   the reagent conditioning means comprises a heating means.

The goal of the claimed invention is also achieved in an automotive vehicle containing a control system according to the invention with the reservoir installed inside or in the proximity of the trunk of the vehicle.

BRIEF DESCRIPTION OF THE DRAWING

Other characteristics and advantages of the present invention will become clear from the following description of an implementation mode of the device according to the invention with reference to the unique FIGURE.

The attached unique FIGURE is a principle diagram of a control system for dispensing reagent in the exhaust line of an internal combustion engine according to a preferred implementation mode of the invention.

DETAILED DESCRIPTION OF THE CLAIMED INVENTION

The dispensing circuit comprises a reservoir 1 for a reagent to be injected, in a dosed manner, into the exhaust gas. For NO_(x) reduction by SCR catalysis, this reservoir can have a volume on the order of 25 liters, or approximately the volume of a wheel, and must be located away from the area under the hood (engine compartment) for instance in an area B, in the proximity of the trunk or in the trunk.

The dispensing circuit comprises an injection means 3 suitable to draw a quantity of reagent from reservoir 1 and to inject it in the exhaust gas. To this end, the injection means 3 comprises, for example, a metering pump controlled in response to the pressure requirements of the injection circuit and an injector for the quantitative requirements of a reagent. In FIG. 1, the arrow starting from pump 3 symbolizes an amount of reagent being pumped to the location where the reagent is injected in the exhaust gas.

As previously indicated a reagent on the basis of urea freezes at a temperature of −11° C. (12° F.). Therefore, the dispensing circuit contains in different points a certain number of reagent conditioning means, for instance a heating device 8 to heat the reagent in the reservoir and auxiliary heating elements 7,9 to heat the conduit between the reservoir 1 and the point of injection in the exhaust line and/or to heat the pump. Temperature sensors are used to determine the heating requirements.

Typically, the dispensing circuit will contain other sensors such as for instance a sensor for the reagent level in the reservoir and a pressure sensor. All sensors together are indicated by reference 2 in FIG. 1.

In addition, the dispensing pump and the injector that are metering precisely the quantity of injected reagent are equipped with specific actuators well known to a person skilled in the art.

All sensors and actuators operate normally in analog mode and the signals received from the sensors are converted in digital signals by an electronic interface 4, mounted for instance on the reservoir. This electronic interface also converts digital signals into analog signals intended for the different actuators.

Interface 4 is connected to the engine control module 5 by a digital connection 6 in the form of a multiplexed connection. In this way, the signals acquired by the dispensing system can be transmitted to the engine control module, or more exactly to a software module in the engine control module, adapted for processing of the signals. In addition, the signals are processed in function of certain known engine parameters in the engine control module, parameters such as for instance the quantity of injected fuel, the quantity of fresh air and of recirculated gas admitted in the cylinders, the engine speed, the required torque, etc. . . . , in other words a series of parameters that allow one to estimate the composition of the exhaust gas, and therefore the potential need to treat these gases, based specifically on tables established in multiple tests performed on engine test stands during which the emission of pollutants was measured.

The same applies to the heaters 7,8 9 for heating the pump, the reservoir and the conduits extending from the reservoir to the injection point, necessary for proper conditioning of the reagent.

According to the invention, the actual processing of the information takes place in the engine control module. The engine control module in turn will send—via the unique multiplexed connection—to the digital interface the signals for the different system actuators. These digital signals are converted as needed to analog signals by the interface. 

1. A system for controlling a reagent dispensing circuit in an exhaust line of an engine, said circuit comprising a reservoir, injection means, reagent conditioning means, sensors suitable for determining parameters representing the status of the dispensing circuit and of the reagent, and command actuators for the conditioning means and the injection means; the command actuators being controlled by a control unit in response to the status of the dispensing circuit and of the reagent and engine parameters as determined by an engine control module; wherein the control unit is integrated in the engine control module and in that the system comprises a digital/analog interface adapted to process the analog signals from sensors and actuators; the control unit being mounted in the proximity of reservoir and connected to the engine control module by a multiplexed digital connection.
 2. The system according to claim 1, wherein said connection is dedicated to the reagent dispensing circuit.
 3. The system according to claim 1, wherein said multiplexed digital connection is a CAN network.
 4. The system according to claim 1 wherein said reagent is a NOx reducing agent.
 5. The system according to claim 1 wherein said system comprises at least one temperature sensor for the reagent in the reservoir.
 6. The system according to claim 1 wherein the reagent conditioning means comprises a heating means.
 7. An automotive vehicle comprising an engine installed in the engine compartment and a control system according to claim 1, wherein the reagent reservoir is installed inside of, or in the proximity of, the trunk of the vehicle. 